There is much evidence supporting the association between the neuroendocrine (NE) phenotype and androgen-independent (AI) growth of prostate cancer (PCa), suggesting the involvement of NE factors in PCa progression. The importance of serotonin and bombesin-like peptides in PCa proliferation and dissemination has been previously demonstrated in this lab. The continuing studies proposed herein will evaluate the role of classical neurotransmitters such as catecholamines, acetylcholine, histamine, excitatory and inhibitory amino acids as well as certain NE peptides on cellular proliferation, invasiveness, as well as in regulating the expression of inflammatory cytokines (interleukin-1 (IL-1) alpha and IL-1 beta) and beta-2 microglobulin in PCa. Although their ligands and/or receptors have been found in PCa, classical neurotransmitters have not been widely investigated as therapeutic targets. Their pharmacology is well-developed with the availability of numerous, receptor sub-type selective, agonists and antagonists. The effect of classical neurotransmitters and their antagonists on collagenase activity, which determines PCa cellular invasiveness, will be tested using the fluorogenic substrate Gelatin DQ. Also, various NE stimulators and inhibitors will be assessed for their effect on the concentration of intracellular calcium ions ([Ca2+]i) using the fluorescent dye, Calcium Green 2. Modulated by mitogens, [Ca2+]i levels are often transducers of the proliferative signal in PCa as well as in other tumor types. Additionally, the effect of neurotransmitters on the expression of three markers of disease progression, IL-1 alpha (PSA-suppression factor), IL-1 beta (AI clonal dominance factor) and beta-2 microglobulin (its loss from the cell-surface is associated with distant metastasis in PCa), will be examined by quantitative RT-PCR and immunoassay. The proposed studies could identify clinically useful inhibitors of PCa development and progression.